## Adding + \$1 for every 1 quanitity, Javascript

I am using this script to update a total cost text box at the end of my form. Here is the cost format script:

<SCRIPT LANGUAGE="JavaScript">

<!-- Begin
function CheckChoice(whichbox)
{
with (whichbox.form)
{
//Handle differently, depending on type of input box.
{
//First, back out the prior radio selection's price from the total:
//Then, save the current radio selection's price:
//Now, apply the current radio selection's price to the total:
hiddentotal.value = eval(hiddentotal.value) + eval(whichbox.price);
}
else
{
//If box was checked, accumulate the checkbox value as the form total,
//Otherwise, reduce the form total by the checkbox value:
if (whichbox.checked == false)
{ hiddentotal.value = eval(hiddentotal.value) - eval(whichbox.value); }
else { hiddentotal.value = eval(hiddentotal.value) + eval(whichbox.value); }
}

//Ensure the total never goes negative (some browsers allow radiobutton to be deselected):
if (hiddentotal.value < 0)
{
InitForm();
}

//Now, return with formatted total:
return(formatCurrency(hiddentotal.value));
}
}

//Define function to format a value as currency:
function formatCurrency(num)
{
num = num.toString().replace(/\\$¦\,/g,'');
if(isNaN(num))
num = "0";
sign = (num == (num = Math.abs(num)));
num = Math.floor(num*100+0.50000000001);
cents = num%100;
num = Math.floor(num/100).toString();
if(cents<10)
cents = "0" + cents;
for (var i = 0; i < Math.floor((num.length-(1+i))/3); i++)
num = num.substring(1,num.length-(4*i+3))+','+
num.substring(num.length-(4*i+3));
return (((sign)?'':'-') + '\$' + num + '.' + cents);
}

//Define function to init the form on reload:
function InitForm()
{
//Reset the displayed total on form:
document.myform.total.value='\$0';
document.myform.hiddentotal.value=0;

//Set all checkboxes and radio buttons on form-1 to unchecked:
for (xx=0; xx < document.myform.elements.length; xx++)
{
if (document.myform.elements[xx].type == 'checkbox' ¦ document.myform.elements[xx].type == 'radio')
{
document.myform.elements[xx].checked = false;
}
}

}

// End -->
</script>

What I am trying to figure out is when I click this box, I need it to add the value to the total amount using the part of the script above but also add +\$1 (1.00) for every quantity of items. So if the value in the QTY text box is: 5 then when this box is clicked add \$10 + \$5.

<input type=text name="quantity" size=3 value=0 priorval=0 price="109.00" onChange="this.form.total.value=checkChoice(this);">

\$10 Shipping: <input type="checkbox" name="\$10_shipping" value=10.00 onclick="countChoices(this);" onChange="this.form.ship_method.value=this.name;" onpropertychange="this.form.total.value=CheckChoice(this);">

TOTAL: <input type="text" name="total" value="" size=8 readonly onFocus="this.blur();">

Any comments or suggestions are greatly apreciated.
Thanks.

~Isaac Lloyd~